// Package games serves emulated games: platform detection from the ROM file
// and per-user save states.
//
// The emulator itself runs in the browser (EmulatorJS); the server's job is to
// identify the platform, hand over the ROM, and keep each user's saves.
package games

import (
	"strings"
)

// Kind is the media kind this module owns.
const Kind = "games"

// Platform is what a ROM extension tells us.
type Platform struct {
	// Name is the human label, e.g. "Super Nintendo".
	Name string
	// Core is the EmulatorJS core id, e.g. "snes". Empty when EmulatorJS has
	// no core for this platform, in which case the UI offers a download
	// instead of a player.
	Core string
}

// platforms maps a file extension to its platform. Extensions are the only
// signal available without parsing ROM headers, and they are reliable enough
// in practice because emulator collections are named consistently.
var platforms = map[string]Platform{
	".nes":  {"Nintendo Entertainment System", "nes"},
	".fds":  {"Famicom Disk System", "nes"},
	".snes": {"Super Nintendo", "snes"},
	".sfc":  {"Super Nintendo", "snes"},
	".smc":  {"Super Nintendo", "snes"},
	".gba":  {"Game Boy Advance", "gba"},
	".gb":   {"Game Boy", "gb"},
	".gbc":  {"Game Boy Color", "gb"},
	".n64":  {"Nintendo 64", "n64"},
	".z64":  {"Nintendo 64", "n64"},
	".v64":  {"Nintendo 64", "n64"},
	".nds":  {"Nintendo DS", "nds"},
	".3ds":  {"Nintendo 3DS", ""},
	".cia":  {"Nintendo 3DS", ""},
	".md":   {"Sega Genesis", "segaMD"},
	".gen":  {"Sega Genesis", "segaMD"},
	".smd":  {"Sega Genesis", "segaMD"},
	".sms":  {"Sega Master System", "segaMS"},
	".gg":   {"Game Gear", "segaGG"},
	".pce":  {"PC Engine", "pce"},
	".ngp":  {"Neo Geo Pocket", "ngp"},
	".ngc":  {"Neo Geo Pocket Color", "ngp"},
	".ws":   {"WonderSwan", "ws"},
	".wsc":  {"WonderSwan Color", "ws"},
	".a26":  {"Atari 2600", "atari2600"},
	".a78":  {"Atari 7800", "atari7800"},
	".lnx":  {"Atari Lynx", "lynx"},
	".col":  {"ColecoVision", "coleco"},
	".int":  {"Intellivision", "intv"},
	".psx":  {"PlayStation", "psx"},
	".ps1":  {"PlayStation", "psx"},
	".cue":  {"PlayStation", "psx"},
	".chd":  {"PlayStation", "psx"},
	".pbp":  {"PlayStation", "psx"},
}

// PlatformFor returns the platform for a file path, or a zero Platform with
// ok=false when the extension is unrecognised.
func PlatformFor(path string) (Platform, bool) {
	ext := strings.ToLower(path)
	if i := strings.LastIndexByte(ext, '.'); i >= 0 {
		ext = ext[i:]
	} else {
		return Platform{}, false
	}
	p, ok := platforms[ext]
	return p, ok
}

// Playable reports whether EmulatorJS can run this platform in the browser.
func (p Platform) Playable() bool { return p.Core != "" }

// Extensions returns every ROM extension the module recognises, for tests and
// diagnostics.
func Extensions() []string {
	out := make([]string, 0, len(platforms))
	for ext := range platforms {
		out = append(out, ext)
	}
	return out
}